Question: Solve for $r$ : $24 + r = 8$
Subtract $24$ from both sides: $ \begin{eqnarray} \\ 24 + r &=& 8 \\ \\ {-24} && {-24} \end{eqnarray} $ $ \begin{eqnarray} \hphantom{24 + r} &\hphantom{=}& \hphantom{8} \\ r &=& 8 {- 24} \\ \end{eqnarray} $ Simplify. $ r = -16$